POS1097 BIOMARKERS OF INFLAMMATION AND JOINT TISSUE TURNOVER CAN HELP IMPROVING THE DIFFERENTIATION BETWEEN OSTEOARTHRITIS AND PSORIATIC ARTHRITIS PATIENTS
Authors: S. S. Groen, S. Holm Nielsen, A. C. Bay-Jensen, M. Rasti, D. Ganatra, K. Oikonomopoulou, V. Chandran
Journal: Annals of the Rheumatic Diseases (2022)

Background Osteoarthritis (OA) is a slow progressive disease characterized by degeneration within the joint cartilage, leading to destruction and dysfunction of the involved joints. Psoriatic arthritis (PsA) is a chronic inflammatory disease manifesting itself in skin lesions and progressive inflammatory changes within the musculoskeletal system, leading to joint damage and functional limitation. Although OA and PsA are considered to be distinct diseases, they share overlapping clinical and inflammatory features that can cause diagnostic challenges. Throughout these inflammatory and degenerative processes in the joint tissues, proteases hold a major role in remodelling of the extracellular matrix (ECM) which results in protein breakdown products released into the synovial fluid (SF). These protein fragments can be quantified in SF as biomarkers of tissue remodelling and may be helpful in characterizing disease-specific or overlapping pathologies between OA and PsA. Objectives Our aim of this study is to measure biomarkers of inflammation and joint tissue turnover in SF to explore the distinct and overlapping pathologies between OA and PsA. Methods SF samples were collected from patients with OA (n=54, mean ±SD age 62.1 ±11.9, 48% female) and patients with PsA (n=59, mean ±SD age 47.8±13.3, 37% female) recruited through Toronto Western Hospital, Canada. Study was approved by the local ethics committee. Biomarkers of inflammation reflecting macrophage activity (VICM) and neutrophil activity (CPa9-HNE) were measured in the SF samples. Moreover, ECM remodelling was assessed in the SF samples by biomarkers quantifying type II collagen formation (PRO-C2), fibronectin turnover (FBN-C), and aggrecan degradation (ARGS). Data were log-transformed and presented as mean ± standard deviation (SD). An ANCOVA corrected for age was applied to test the difference between biomarker levels across the two patient groups and a p-value below 0.05 was considered significant. Area under the receiver operating characteristic (ROC) curve (AUC) analysis was performed to describe the discrimination accuracy of each biomarker between the two patient groups. Results PsA patients presented significantly higher levels of macrophage; VICM, activity compared to OA (p&lt;0.001, Figure 1A). On the other hand, OA patients demonstrated increased type II collagen formation and aggrecan degradation compared to PsA (p&lt;0.001, Figure 1C, E). Interestingly, no significant difference in biomarkers levels of neutrophil activity and fibronectin remodelling was observed between the two disease groups. Moreover, VICM, PRO-C2, and ARGS showed high distributional difference between OA and PsA patients with an AUROC=0.915 (p&lt;0.001, Figure 1F), AUROC=0.737 (p&lt;0.001, Figure 1G), and AUROC=0.725 (p&lt;0.001, Figure 1H), respectively. Conclusion PsA patients demonstrated higher macrophage activity in the SF compared to the OA patients, while higher levels of cartilage formation and degradation were observed in OA patients compared to PsA. No differences between OA and PsA were observed in neutrophil activity and fibronectin turnover, which may mirror the clinical difficulty in telling the two arthritides apart. Identifying the unique characteristics of the pathological processes underlying the two diseases may improve diagnosis and allow for the precise management of both OA and PsA patients. Disclosure of Interests Solveig Skovlund Groen: None declared, Signe Holm Nielsen Employee of: Signe is employed by Nordic Bioscience, Anne-Christine Bay-Jensen Shareholder of: Anne C. Bay-Jensen holds stock in Nordic Bioscience, Employee of: Anne C. Bay-Jensen is employed by Nordic Bioscience, Mozhgan Rasti: None declared, Darshini Ganatra: None declared, Katerina Oikonomopoulou: None declared, Vinod Chandran: None declared